The invention relates to an electric-motor drive mechanism according to the preamble to the main claim.
The reference DE 43 37 390 C2 has disclosed an electric-motor drive mechanism with an electronic module which has a circuit for supplying power to the electric motor of the drive mechanism. The brush guide of a commutation device of the electric motor is connected to a supporting component of the electronic module constituted by an electric chassis. The supply of power to the brushes of the commutation device takes place by means of strip conductors, which are not a component of a printed circuit board of the electronic module.
Furthermore, electric-motor drive mechanisms with brush holders have been disclosed, which has a plug housing with connector plugs formed onto it. The brush holders are disposed inside the electric motor of the drive mechanism. Printed circuit boards with Hall sensors are disposed on the brush holders and are supplied with energy via inserted strip conductors that electrically contact the connector plugs.
This apparatus has the disadvantage that the attachment of printed circuit boards to the commutator is costly from a technical manufacturing standpoint and the printed circuit boards can only be replaced with difficulty in the event of the defect. Furthermore, the electronic components on the printed circuit board are subjected to the rough environmental conditions inside the motor. On the one hand, the temperature inside the motor is increased, on the other hand abrasion of the carbon brushes, the armature shaft bearing, or the armature shaft itself produced by the motor operation can come to bear on the electronic components and can trigger malfunctions and short-circuits.
The invention, with the features of the main claim, has the advantage that a set of motor control and output electronics, with the exception of one or several magnetic field sensors, is disposed completely outside the electric motor. Since the magnetic field sensors are not disposed on the electronics mounting plate as in the previously disclosed embodiments, the tolerances that must be maintained in the installation of the electronics mounting plate are less critical than in the previously disclosed embodiments. Furthermore, a modular design is possible since different control electronics can be provided for the same motor on different electronics mounting plates without changing the motor concept and a new set of electronics can be installed by replacing the electronics mounting plate. If the electronics mounting plate is disposed outside the motor compartment, it is considerably better protected against the abrasion of the electric motor. In particular, Hall sensors or magnetoresistive sensors are used as the magnetic field sensors.
The term inserted strip conductors is understood to mean that these strip conductors are not components of a printed circuit board. Instead, they are used to produce the contact between a printed circuit board and an electronic component that is spaced apart from it. They are comprised, for example, of metal strips which can constitute separate components or can be applied to other components of the electric motor.
Advantageous improvements and updates of the invention ensue from the dependent claims.
The electric-motor drive mechanism according to the invention can be produced in a particularly inexpensive manner if the electronics mounting plate has an essentially rectangular outline. In this case, standard printed circuit boards can be used. It is no longer necessary to expensively design the outline of the printed circuit boards based on the contour of the pole pot housing. Smaller deviations from the rectangular form can be simply and inexpensively manufactured.
In a favorable embodiment, the electronics mounting plate is disposed lateral to the rotation axis of the motor armature shaft. This disposition is particularly space-saving since the electronics housing can then turn out to be small.
The pole pot housing of electric motor is advantageously sealed in relation to the electronics mounting plate. As a result of this measure, the electronics mounting plate is even better protected against the abrasion of the electric motor. Also, moisture and other substances are effectively prevented from penetrating into the electric motor.
If the support tapers at the transition to the brush holder and the inserted strip conductor(s) are integrated into the taper, then they are guided from the pole pot housing to the electronic mounting plate so that they are protected in relation to the outside without additional measures. In addition to the mechanical protection, the accommodation in the brush holder/support, also effectively protects them electrically. By means of the taper between the support and the brush holder, the support can move the electronics mounting plate elastically out of the way within certain limits when there are forces engaging the outside of the electronics housing, as a result of which the danger of breakage is reduced.
In one embodiment of the invention, two magnetic field sensors are provided and the brush holder and the support have an at least approximate reflective axis lateral to the axis of the motor armature shaft in the plane of the electronics mounting plate. The magnetic field sensors are disposed in the circumference direction in relation to the magnetic wheel at approximately equal angles in relation to the center point of the magnetic wheel and the reflective axis. The use of two speed sensors permits the determination of the rotation direction through evaluation of the phase shift of the sensor signals. On the whole, this embodiment has the advantage that the inserted strip conductors can be disposed in a particularly space-saving manner.
The space-saving disposition can be further improved if the at least one magnetic field sensor is disposed tangential to the edge of a recess of the brush holder for containing the magnetic wheel, the inserted strip conductors have contact ends to the magnetic field sensor that are disposed oriented toward the brush holder, and contact strips of the inserted strip conductors are guided between the contact ends and the electronics mounting plate from the edge of the recess to the edge of the brush holder and from the edge of the brush holder onward, extend essentially parallel to the contour of the brush holder or the support and parallel to the plane of the electronics mounting plate. By means of this special guidance of the inserted strip conductors, moreover, the mechanical stability of the brush holder/support is improved and the breakage susceptibility is reduced since the strip conductors constitute a skeleton-like support structure inside the brush holder and the support. As a result of their parallel routing, the electrical signals transmitted from them are less susceptible to incoming interference signals.
Another advantageous improvement is achieved if second inserted strip conductors for supplying power to the brushes are at least partially integrated into the brush holder and are disposed between the support and the brush holder. In this instance, separate electrical routings from the electronics housing into the motor are no longer necessary since all of the contact strips to the motor extend inside the brush holder or the support.
Further advantageous improvements and updates of the invention ensue from the other dependent claims and in conjunction with the subsequent description.